Recently, as nonvolatile storage devices, electrically rewritable variable resistance elements such as ReRAM (resistance random access memory) and PRAM (phase change random access memory) have been drawing attention.
The variable resistance element used as a storage element of the nonvolatile storage device includes a structure in which an electrode (including semiconductor material), a variable resistance material such as metal oxide (binary or ternary), and an electrode (including semiconductor material) are stacked.
Variable resistance elements are classified into the bipolar type and the unipolar type. In the bipolar type, the high resistance state and the low resistance state are switched by changing the polarity of the application voltage. In the unipolar type, the high resistance state and the low resistance state are switched by controlling the voltage and the application time without changing the polarity of the application voltage. To the variable resistance element, a rectifying element is connected. The rectifying element is used so as to apply a voltage in a prescribed direction to the variable resistance element selected for data writing and reading, and not to apply the voltage in the prescribed direction to the non-selected variable resistance element. In such nonvolatile storage devices, further improvement in the characteristics of the rectifying element is desired.